Coffee might give you a short-term perk (although not if you're a habitual coffee drinker) because it blocks adenosine, the main compound in your brain that makes you sleepy. But it's a stimulant, so drinking too much in the afternoon is likely to affect your sleep at night.

There's no hard-and-fast rule for exactly when to cut off your caffeine supply because everyone metabolises it differently, says Dr Liora Kempler, sleep psychologist at the Woolcock Institute of Medical Research.

But the half-life of coffee is about five hours, so for most people it's wise to steer clear of caffeine about five hours before bed, she says. (Dr Liora herself stops at 2pm.)

The verdict: It's best to steer clear of caffeine in the afternoon, especially for several hours before bedtime.

Option three: Stretching your legs

Image Not only will you feel more energised going for a quick walk, you'll also feel extra smug afterward.(ABC Life: Nathan Nankervis)

If you work in an office or another sedentary environment, your afternoon feelings of fatigue might be caused by reduced blood flow.

One way to tackle that drowsiness is a quick burst of energy, which "gets the blood flowing, and assists the muscle in using the glucose and fats," says Professor David Dunstan, head of the Physical Activity Laboratory at the Baker Heart and Diabetes Institute.

Dr Dunstan has led studies into the effects of prolonged sitting on fatigue and cognition, specifically with overweight or obese people, or those with type 2 diabetes.

"Three-minute micro bursts of activity, which could include walking around the office", may help combat mid-afternoon fatigue, says Dr Dunstan.

If going for a walk isn't possible in your workplace, you could also try "body exercises like squatting-type exercises, calf raises and hip inflections for three minutes". That method showed substantial improvement for the subjects of one of Dunstan's studies.

Keep in mind, though, that exercising in the later part of the day can make it harder to sleep at night. This is because exercise heats up your body, and you need a falling body temperature to fall asleep.

For that reason, it's best to avoid high intensity exercise in the last six to eight hours of the day if you can help it, Dr Kempler says.

The verdict: A short walking break is a great option to combat your afternoon drowsiness — better than coffee and, if you work during the day, more viable than a short nap.